Childhood bacterial meningitis in Japan

Haemophilus influenzae type b (Hib) vaccines currently are not used in Japan, but interest in preventing H. influenzae disease by immunization has grown. We performed a retrospective survey for bacterial meningitis in 6 prefectures of Japan. Questionnaires requested the age, sex, clinical outcome and identity of the etiologic organism, if known, of all patients with meningitis younger than 16 years of age who were admitted during calendar year 1994. Of 876 hospitals within the 6 study prefectures, 363 (41.4%) returned a completed questionnaire. There were 1769 cases of meningitis reported, of which 160 (9%) were considered bacterial in origin. H. influenzae was the most common cause of bacterial meningitis, accounting for 68 cases (43%). Sixty-six cases (97%) of H. influenzae meningitis occurred in children 4 years of age or younger, and 27 (40%) occurred in children <1 year of age. Calculated incidence rates based on the population of children 4 years of age or less for each prefecture ranged from 3.4 to 9.9 cases per 100000 (mean, 4.7 cases/100000). H. influenzae is the most common cause of meningitis in Japan, and the estimated incidence rates from this study are very similar to those previously reported from Japan. More comprehensive, prospective surveillance studies will be needed to define better the incidence of Hib meningitis and to aid in making rational decisions regarding the use of Hib vaccination in Japan.